An Australian man has been arrested in the United States over the Madeleine Pulver collar-bomb hoax on Sydney's north shore two weeks ago.

Eighteen-year-old Ms Pulver spent 10 hours with a fake bomb chained to her neck at her family's Mosman home.

Paul "Doug" Peters was arrested by FBI agents, after a request by New South Wales detectives, at his ex-wife's home in the US town of La Grange, north-east of Louisville in Kentucky early this morning (Australian time).

Police say 50-year-old flew out of Australia on August 8, five days after Ms Pulver was targeted.

Assistant Commissioner David Hudson says the man was an Australian citizen who travelled for business between Sydney and the US, and had family in both countries.

"He's an Australian citizen, known to commute between here and the United States," he said.

Assistant Commissioner Hudson says police are confident the man is the person who broke into the Pulvers' house and shackled Madeleine to the fake bomb collar.

"We'll be alleging through the courts that the suspect we've arrested this morning was responsible for entering the Pulver home and placing the device around Madeleine's neck," he confirmed.

The man, who lived in Sydney when he was in Australia, had been in Australia for about six weeks before the attack.